Tokyo (CNN) -- Japan has slapped new restrictions on green tea and plums from areas around the Fukushima Daiichi nuclear power plant because of lingering radioactive contamination from the ongoing disaster there.

The latest government bans were prompted by the discovery of radioactive cesium-137 and -134 at concentrations higher than Japanese standards allow, Chief Cabinet Secretary Yukio Edano told reporters Thursday.

Both are nuclear waste products: cesium-137 has a half-life of 30 years, while cesium-134 has a two-year half-life.

The government has now forbidden the shipment of both fresh and dried green tea -- normally touted for its health benefits -- from Ibaraki Prefecture, southwest of the plant; from six towns in Chiba Prefecture and six towns in Kanagawa Prefecture, near Tokyo; and two in Fukushima Prefecture, where the crippled plant is located.

In addition, Edano said, the government has banned the shipment of plums from three towns in Fukushima.

The moves come nearly three months into the crisis at Fukushima Daiichi, the worst nuclear accident since the 1986 Chernobyl disaster. One of three operating reactors at the plant melted down after the March 11 earthquake and tsunami, and the other two suffered extensive damage to their radioactive cores.

Though no deaths have been attributed to the accident, the resulting contamination has forced authorities to evacuate more than 100,000 people from towns surrounding the plant. In addition, restrictions on various agricultural and fisheries products have devastated Japanese farmers and fishermen since the disaster began, though some of those bans have been lifted in recent weeks.

The plant's owner, the Tokyo Electric Power Co., has laid out a timetable for restoring normal cooling systems and fully shutting down the reactors by January. But Prime Minister Naoto Kan cautioned that people may not be allowed to return home immediately, "even if these prospects are realized."

"We might have to continue monitoring, and we need to maybe decontaminate," said Kan, whose government survived a no-confidence vote Thursday spurred by complaints about his handling of the twin crises. "And for that, there may be some more time needed."

The disaster has spurred Japan to rethink its commitment to nuclear energy and tighten safety standards for existing plants. A preliminary report from the International Atomic Energy Agency concluded this week that Japan underestimated the risks its nuclear installations faced from tsunamis, like the one that swamped the Fukushima Daiichi plant and knocked out its cooling systems.

But the U.N. nuclear watchdog agency declared the country's response to the disaster "exemplary," praising Tokyo Electric's operators for their "brave and sometimes novel" efforts to contain the crisis.